The National Cancer Institute estimates 178,480 new breast cancer cases will be reported in 2007. While many environmental factors have been suggested to play a role, the mechanisms underlying these complex interactions have not been identified. Alcohol consumption is listed as a risk factor for breast cancer by the American Cancer Society, and abstinence from drinking alcohol during pregnancy is undisputedly advised. However, many women who drink alcohol are not aware of their pregnancy until the second trimester, while others continue to drink while pregnant. The broad, long-term goal of this proposal is to identify the mechanisms by which alcohol exposure in utero acts to alter susceptibility to breast cancer using a rodent model. The proposed study hypothesizes that alcohol exposure in utero will increase circulating estrogen leading to increases in components of the IGF-I growth factor signaling system within the mammary gland. This alteration in growth factor expression will result in an increased proliferation of cells in the mammary gland, leading to increased susceptibility to a mammary carcinogen. To determine if alcohol exposure in utero affects carcinogen-induced mammary cancer and growth factor expression, three groups of pregnant Sprague dawley rats will be fed a liquid 6.37% alcohol diet, an isocaloric liquid diet, or ad lib rat chow, and female pups from these dams will be administered a carcinogen to induce mammary tumors. Tumor size, burden, and latency will be monitored throughout the study. At termination of the study, serum IGF-I concentrations will be measured and steroid hormone and growth factor components will be analyzed in both tumorous and normal mammary tissue. To determine if alcohol exposure in utero alters circulating estrogen levels as well as mammary gland morphology, pups from the same study design will be used without receiving carcinogen. Offspring will be sacrificed during proestrous. Serum estradiol will be measured, and mammary tissue will be collected for wholemount analysis. The third objective in this study is to identify molecular mechanisms occurring in the in the mammary epithelial cells that increase mammary susceptibility to tumorigenesis. Primary mammary epithelial cells will be isolated from alcohol-exposed pups, and pups not exposed to alcohol. Interactions between estrogen, EGF, and IGF-I receptors and the involvement of Src Kinase, will be assessed by co-immunoprecipitation and western blot analysis. Identifying the mechanisms that underlie how alcohol exposure in utero affects carcinogenesis could lead to breakthroughs in understanding how environmental exposure in utero alters life-time susceptibility to disease.